Over 8 million children and families in the United States today live in poverty (U.S. Census Bureau, 2017a). Children are disproportionately affected by poverty, with 37% of children experiencing at least one spell of poverty in childhood (Ratcliffe & McKernan, 2010). Poverty is associated with deleterious child outcomes, including learning disabilities, health problems, and elevated levels of exposure to family conflict (e.g., intimate partner violence) (Brooks-Gunn & Duncan, 1997; Odgers & Adler, 2018). Poverty is also linked with negative fathering behaviors, such as harsh parenting that involves hostility towards the child (McLoyd, 1990). Further, research has shown associations between being socioeconomically disadvantaged and fathers becoming increasingly nonresidential, especially among low-income, unmarried families (Mincy, Jethwani, & Klempin, 2014). Today, 1 out of 5 children live in households where the father is nonresidential, and approximately 30% of these single-mother headed households live in poverty (Livingston, 2018).Poverty is officially defined and measured using a set of income thresholds that vary by family structure (U.S. Census Bureau, 2017b). It is an inadequate measure of families? economic instability because it relies on an outdated threshold and fails to capture families that may have some income but still experience material hardship (Boushey, Brocht, Gundersen, & Bernstein, 2001). Although low-income fathers financially contribute to their families, less is understood about how such contributions?especially those outside the formal child support system for nonresidential fathers?are linked with reducing families? material hardship and, ultimately, strengthening positive father-child interactions. The proposed study addresses this gap.The proposed study builds on an adapted version of the family stress model to investigate two primary questions: (1) Do two distinct aspects of families? economic stability, specifically material hardship and father-contributed family income, predict father involvement (e.g., engagement with child)? and (2) Does father?s residential status moderate the associations of families? economic stability and father involvement? Further, a secondary question will be examined: (3) Do father?s and mother?s mental health and co-parenting serve as mediators in the associations of low-income families? economic stability and father involvement?The proposed study draws data from the Building Strong Families (BSF) project, a large-scale healthy marriage program for low-income, unmarried couples with young children. The results of the proposed studies will elucidate mechanisms by which economic stability promotes father involvement in low-income, unmarried families, as well as help identify targets of intervention. Such results will inform current/future Healthy Marriage and Responsible Fatherhood policy and program initiatives aimed at improving the lives of children and parents, promoting economic stability, building healthy relationships, and strengthening positive father-child interactions.